1. Field of the Invention
The present invention relates to a fluid filtering apparatus used for filtering oil or the like for an automobile, and especially to a filter element of such a fluid filtering apparatus.
2. Description of the Related Art
As such a kind of apparatus there has already been known a filtering apparatus in which a tubular filter element received in a filter case, and the opposite ends of the filter element are sealed so as to divide the inside of the filter case into a dirty-side zone located on the outer peripheral side of the filter element and a clean-side zone located on the inner peripheral side thereof.
Such a filtering apparatus is provided with sealing members having a disc-shape disposed on the opposite ends of the filter element, respectively, in order to prevent fluid in the dirty-side zone from bypassing the filter element to flow into the clean-side zone. European Patent Publication No. 447875B1 discloses a structure in which the sealing member made of thermoplastic or the like and the end of an element body made of filter paper or the like are joined to each other by ultrasonic fusion. The joining structure utilizing the ultrasonic fusion makes it possible to reduce the steps and period of time required to join them in comparison with the other joining structure using hot melt adhesive or an ordinary adhesive agent. Incidentally, Japanese Patent Provisional Publication No. H6-31119 discloses a joining method in which thermoplastic resin contained in filtering members is fused by ultrasonic vibration so as to join these filtering members.
However, when the ultrasonic fusion is applied to the entire surface of the sealing member, the sealing member is hardened through a molten product caused by a fusing step, resulting in loss of resiliency of the sealing member over its entire surface. This deteriorates the function of the sealing member serving as packing, thus making it impossible to realize a sealing structure for bringing the sealing member into close contact with the other member.